﻿<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Server-Side Images with GoJS -- Northwoods Software</title>
  <!-- Copyright 1998-2020 by Northwoods Software Corporation. -->
  <script src="../release/go.js"></script>
  <script src="goIntro.js"></script>
</head>
<body onload="goIntro()">
<div id="container" class="container-fluid">
<div id="content">
<h1>Creating Images on the Server</h1>
<p>
  It may be useful for many applications to create images of Diagrams with <b>GoJS</b>, and this page details some of the options for such a task.
</p>
<h2 id="Puppeteer">Puppeteer</h2>
<p>

<a href="https://github.com/GoogleChrome/puppeteer">Puppeteer</a> is a Node library which provides a high-level API to
control headless Chrome. We can use it to create images server-side. If you have Node and npm installed you can
install it with <code>npm install puppeteer</code>.

<p>
The following code is a small example using Puppeteer.
If you saved the JavaScript as <code>puppet.js</code> and run it with node (<code>node createImage.js</code>)
it demonstrate creating two images: One from the Diagram called <code>gojs-screenshot.png</code> and one of the HTML page
called <code>page-screenshot.png</code>.
The Diagram code in the sample is the same as that in the <a href="../samples/minimal.html">Minimal sample</a>.
</p>

<pre class="lang-js">
// This example loads the GoJS library then adds HTML from scratch and evaluates some JavaScript,
// then creates a screenshot of Diagram with makeImageData, plus a screenshot of the page.

const puppeteer = require('puppeteer');
const fs = require('fs');

const parseDataUrl = (dataUrl) => {
  const matches = dataUrl.match(/^data:(.+);base64,(.+)$/);
  if (matches.length !== 3) {
    throw new Error('Could not parse data URL.');
  }
  return { mime: matches[1], buffer: Buffer.from(matches[2], 'base64') };
};

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();

  // Point to a version of go.js, either a local file or one on the web at a CDN
  await page.addScriptTag({
    url: 'https://unpkg.com/gojs'
    // path: '../../release/go.js'
  });

  // Create HTML for the page:
  page.setContent('&lt;div id="myDiagramDiv" style="border: solid 1px black; width:400px; height:400px"&gt;&lt;/div&gt;');

  // Set up a Diagram, and return the result of makeImageData:
  const imageData = await page.evaluate(() => {
    var $ = go.GraphObject.make;

    var myDiagram = $(go.Diagram, "myDiagramDiv",
      {
        "animationManager.isEnabled": false,
        "undoManager.isEnabled": true  // enable undo &amp; redo
      });

    // define a simple Node template
    myDiagram.nodeTemplate =
      $(go.Node, "Auto",  // the Shape will go around the TextBlock
        $(go.Shape, "RoundedRectangle", { strokeWidth: 0 },
          new go.Binding("fill", "color")),
        $(go.TextBlock,
          { margin: 8 },
          new go.Binding("text", "key"))
      );

    myDiagram.model = new go.GraphLinksModel(
      [
        { key: "Alpha", color: "lightblue" },
        { key: "Beta", color: "orange" },
        { key: "Gamma", color: "lightgreen" },
        { key: "Delta", color: "pink" }
      ],
      [
        { from: "Alpha", to: "Beta" },
        { from: "Alpha", to: "Gamma" },
        { from: "Beta", to: "Beta" },
        { from: "Gamma", to: "Delta" },
        { from: "Delta", to: "Alpha" }
      ]);

    return myDiagram.makeImageData();
  });

  // Output the GoJS makeImageData as a .png:
  const { buffer } = parseDataUrl(imageData);
  fs.writeFileSync('diagram-screenshot.png', buffer, 'base64');

  // Output a page screenshot
  await page.screenshot({ path: 'page-screenshot.png' });
  await browser.close();
})();
</pre>

<p>
  You can also use Puppeteer to fetch live HTML pages and do the same operations:
</p>


<pre class="lang-js">
// This example loads a web page with a GoJS diagram,
// then creates a screenshot of the Diagram with makeImageData, plus a screenshot of the page.

const puppeteer = require('puppeteer');
const fs = require('fs');

const parseDataUrl = (dataUrl) => {
  const matches = dataUrl.match(/^data:(.+);base64,(.+)$/);
  if (matches.length !== 3) {
    throw new Error('Could not parse data URL.');
  }
  return { mime: matches[1], buffer: Buffer.from(matches[2], 'base64') };
};

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  // This does not have to be a page on the web, it can be a localhost page, or file://
  await page.goto('https://gojs.net/samples/orgChartEditor.html', {
    waitUntil: 'networkidle2' // ensures images are loaded
  });


  const imageData = await page.evaluate(() => {
    window.myDiagram.animationManager.stopAnimation();
    return window.myDiagram.makeImageData({
      background: window.myDiagram.div.style.backgroundColor
    });
  });

  // Output the GoJS makeImageData as a .png:
  const { buffer } = parseDataUrl(imageData);
  fs.writeFileSync('diagram-screenshot.png', buffer, 'base64');

  // Output a page screenshot
  await page.screenshot({ path: 'page-screenshot.png' });
  await browser.close();
})();
</pre>


</div>
</div>
</body>
</html>
